[Vala] Get correct PID after sudp

[Christian Capasso <capasso912 gmail com>]

Hi,

I'm using Process.spawn_async() to launch a process that requires
administrator privileges. This function returns the PID linked to the sudo
command, which is different from the real PID of the command that I
launched.

For example, if the process launched is "dd", I get a different PID, which
corresponds to the PID assigned to the sudo command and not to "dd".

Thank you very much in advance,
Christian.